The Supreme Court ruled yesterday that a university student expelled for "academic" reasons has no right under the Constitution to a hearing of any kind or to an opportunity to respond to allegations made against her.

The nine justices held unanimously that the University of Missouri accorded Charlotte Horowitz of the Disrict of Columbia "at least as much due process" as the 14th Amendment requires when it dismissed her five days before she was to graduate from the School of Medicine in Kansas City in 1973.

A central issue in the case was the school's allegations that Horowitz repeatedly failed to maintain acceptable personal hygiene, as evidenced by unkempt hair, dirty fingernails and yellowed lab coats; was late, and didn't get along well with physicians, patients and fellow students.

At the same time, the university freely acknowleged her academic brilliance. In the Medical College Admissions test, for example, she scored in the top 1 percent.

The school said that from the time it was established its goal was to turn out physicians who would perform well not only in taking a case history or diagnosing an illness, but also in making a proper impression on patients and in other aspects of clinical practice.

Horowitz had scant interest in cultivating a bedside manner: she planned to take a research post at the University of North Carolina that was promised to her on condition she graduate. She has been unemployed for 4 1/2 years, blaming the "stigma" of expulsion.

Despite the 9-to-0 vote to reverse a decision by the 8th U.S. Circuit Court of Appeals that the university had denied Horowitz rights guaranteed by the Constitution, only four justices joined Justice William H. Rehnquist in the opinion for the court.

"A school is an academic institution, not a courtroom or administrative hearing room," he wrote for the five-member majority. "We decline to further enlarge the judicial presence in the academic community . . ."

Rehnquist distinguished between a violation of "valid rules of conduct" and an "academic dismissal," that calls for "far less stringent procedural requirements." The record "leaves no doubt" that Horowitz was dismissed for "pure academic reasons," he said.

Justice Thurgood Marshall declined to join the majority opinion because it suggested that Horowitz "was entitled to even less procedural protection than she received."

He also rejected the characterization of the reasons for a dismissal as "academic" or "disciplinary" as "relevant to resolution of the question of what procedures are required by the due process clause." So did Justice Harry A. Blackmun, in a third opinion joined by Justice William J. Brennan Jr.

In addition, Blackmun, said there was no need for the majority -- and for one of its members. Justice Lewis F. Powell Jr., in a separate opinion -- "to indulge in the arguments and counter-arguments as to the extent or type of procedureal protection" required by the 14th Amendment. Justice Byron R. White, in a fifth opinion, agreed.

In Kansas City, Arthur A. Benson III, Horowitz's lawyer, said that the Rehnquist opinion "appears to give medical-school educators unbridled discretion in dealing with students. By attaching an "academic" label to any reason for dismissing a student, the school insulates itself from a judicial review of the propriety of its decision."

Similarly, the American Civil Liberties protested that Horowitz clearly faced "charges of personal misconduct as opposed to academic deficiency."

The majority "reached out" to decide issues "not really in the case," said the ACLU's Joel Gora. "Concern about judicial interference in academic judgments was not before the court."

That view reflected Justice Marshall's protest that the case provided "no legitimate opportunity to consider whether 'far less procedural requirements'" were required. The court decided "an issue not presented," he charged.

Marvin Wright, an attorney for the school, said, "We're very, very pleased. . ."

A spokesman for the American Association of American Medical Colleges said the ruling "apparently affirms the authority of the faculty to determine who can meet the responsibility" that goes with having an MD degree.

Horowitz could not be reached at her home in Northwest Washington. She is, her lawyer said, "obviously disappointed."

Her troubles began in 1971, her first year at the school, when several faculty members expressed dissatisfaction with her performance. But the Council on Evaluation, a faculty-student body, recommended her advancement -- on a probationary basis -- to her second and final year.

Faculty dissatisfaction persisted in 1972. Her adviser, for example, rated her skills in clinical patient-oriented settings "unsatisfactory."

In the middle of the final year, the council reviewed her situation and concluded not only that she should not be considered for graduation in June 1973 but also that she be dropped by the school unless she showed "radical improvement."

As an "appeal" of the decision not to let her graduate, the school relented to let Horowitz take a set of oral and other examinations and had her spend a substantial amount of time with seven practicing physicians who then were asked for their counsel.

Two recommended she be graduated on schedule, two said she should be expelled at once, and three recommended that she not be allowed to graduate but be put on probation.

In the end, the council recommended, and higher school authorities endorsed, her dismissal.

She complained that by seriously impairing her opportunity either to continue her medical education or get a job, the dismissal deprived her of her "liberty."

Horowitz alleged that she was measured by strict, prejudicial standards because she is a woman, Jewish and of a physical appearance some find unattractive. The trial judge, in ruling against her, found in the record "no evidence" that these factors led to an evaluation by standards any different than those applied to other students.